Magnetic head actuator with centered deviation

ABSTRACT

A magnetic disk device comprises a magnetic disk in which a data zone is formed. An actuator has a voice coil and a head slider carrying a magnetic head, the actuator being swung to move the magnetic head over the disk between an innermost position of the data zone and an outermost position of the data zone. A magnet has a magnetization center and is opposed to the voice coil so that a voice coil motor which swings the actuator is formed, the magnet having a north pole and a south pole confronting each other via the magnetization center. The magnetic disk device is provided so that a deviation of a center of the voice coil from the magnetization center when the magnetic head is in the innermost position of the data zone is substantially equal to a deviation of the center of the voice coil from the magnetization center when the magnetic head is in the outermost position of the data zone.

This applications is a Divisional of prior application Ser. No.10/901,214 filed on Jul. 29, 2004 now U.S. Pat. No. 7,336,448, thecontents being incorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese application No. 2004-054244, filed on Feb. 27, 2004,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a magnetic disk device, andmore particularly to a magnetic disk device which includes an actuatormoving the magnetic head between the innermost positions of the datazone of the magnetic disk and the outermost position of the data zonethereof.

2. Description of the Related Art

In a magnetic disk device that performs recording or reproduction ofinformation to the magnetic disk, it is necessary to avoid wearing ofthe head slider (the magnetic head) by the contact between the headslider and the magnetic disk surface.

Therefore, the contact start-stop (CSS) method is adopted in which thehead slider contacts the disk surface only at the time of non-operationof the magnetic disk device, and the head slider is raised over thesurface of the magnetic disk during its rotation at the time ofoperation of the magnetic disk device (or the time of recording orreproduction of information).

In the magnetic disk device of the CSS method, the head slider whichcarries the magnetic head which performs recording or reproduction ofinformation to the magnetic disk surface is raised by receiving the airflow which is created by the rotation of the magnetic disk at the timeof operation of the magnetic disk device.

And when recording or reproducing information to the magnetic disk, thehead slider is moved with the actuator while being raised over thesurface of the rotating magnetic disk and the head slider is positionedon the predetermined track of the magnetic disk.

Specifically, a data zone is formed in the magnetic disk, and themagnetic head is moved between the innermost position of the data zoneof the disk and the outermost position of the data zone of the disk bythe actuator. For example, this is known from Japanese Laid-Open PatentApplication No. 2001-035103.

On the other hand, when the magnetic disk device is in the non-operatingstate, the head slider is located on the CSS zone which is formed in thesurface of the magnetic disk. Moreover, the rotation of the magneticdisk is stopped when the magnetic disk device is in the non-operatingstate, the air flow which serves to raise the head slider is notcreated, and the head slider is in contact with the CSS zone of thedisk.

The CSS zone may be formed at either the disk inner peripheral positionthat is located inside the innermost position of the data zone of themagnetic disk, or the disk outer peripheral position that is locatedoutside the outermost position of the data zone of the magnetic disk.Usually, the CSS zone is formed at the disk inner position.

A description will now be given of a conventional magnetic head device100 by using FIG. 1 through FIG. 7.

FIG. 1 is a plan view of the conventional magnetic head device 100 whenthe head slider is located in the innermost position of the data zone ofa magnetic disk. FIG. 2 is a plan view of the conventional magnetic headdevice 100 when the head slider is located in the outermost position ofthe data zone of the magnetic disk. Only the portion of the conventionalmagnetic head device 100 near the actuator 122 is illustrated.

As shown in FIG. 1 and FIG. 2, the actuator 122 which supports the headslider 104 on which the magnetic head is carried is rotatably supportedon the supporting shaft 140 such that the actuator 122 is capable ofbeing swung around the center of the supporting shaft 140.

The head slider 104 is formed with the support arm 124 and the supportspring 125 in the front-end portion of the actuator 122 which is locatedin the front direction from the supporting shaft 140.

On the other hand, in the rear-end portion of the actuator 122 which islocated in the rear direction from the supporting shaft 140, the coilarm 152 is formed with the actuator 122. The voice coil 151 is mountedon the coil arm 152.

As shown in FIG. 4, the voice coil 151 is provided so that the voicecoil 151 is located in the magnetic field which is created with theupper magnet 156 provided on the undersurface of the upper yoke 154 andthe lower magnet 155 provided on the upper surface of the lower yoke153.

The voice-coil motor (VCM) 123 is constituted to swing the actuator 122by means of the voice coil 151, the lower yoke 153, the upper yoke 154,the lower magnet 155, and the upper magnet 156.

Moreover, the magnetic disk 101 is rotated at the predeterminedrotational speed by the spindle motor 112.

The data zone 132 is formed in the magnetic disk 101. Therefore, thehead slider 104 is moved between the outermost position “Po” of the datazone 132 of the disk and the innermost position “Pi” of the data zone132 of the disk. Moreover, the CSS zone 131 is further formed in thedisk inner peripheral position that is located inside the innermostposition Pi of the magnetic disk 101.

FIG. 3 is an enlarged view of the actuator 122 which is provided in theconventional magnetic head device 100. As shown in FIG. 3, the voicecoil 151 which constitutes part of the voice-coil motor 123 is attachedto the coil arm 152, and the voice coil 151 is arranged in a generallytrapezoidal configuration. The actuator 122 of FIG. 3 is provided sothat the intersection of the extension lines (indicated by the arrows B1and B2 in FIG. 3) of the side section coils 151A and 151B of the voicecoil 151 is in agreement with the rotation center (or the center of thesupporting shaft 140) of the actuator 122.

FIG. 6 shows the composition of the upper and lower magnets 155 and 156which constitute part of the voice-coil motor 123 in the conventionalmagnetic head device 100. In FIG. 6, only the lower magnet 155 is shownfor the sake of convenience of illustration, but the upper magnet 156which has the same composition as the lower magnet 155 is also provided.

The lower magnet 155 is composed of the north-pole magnet section 155Nand the south-pole magnet section 155S, and this north-pole magnetsection 155N and this south-pole magnet section 155S confront each other(hereinafter, the position where the north-pole magnet section 155N andthe south-pole magnet section 155S confront each other is called themagnetization center 158).

Conventionally, the magnet 155 is provided such that the north-polemagnet section 155N and the south-pole magnet section 155S are arrangedin a symmetrical formation with respect to the magnetization center 158.That is, the deviation (which is indicated as the rotational angle TN inFIG. 6) of the right side section of the lower magnet 155 from themagnetization center 158 and the deviation (which is indicated as therotational angle TS in FIG. 6) of the left side section of the lowermagnet 155 from the magnetization center 158 are equal to each other(TN=TS).

In addition, the stoppers 127A and 127B are arranged at both the sidepositions of the voice-coil motor 123, and the voice-coil motor 123 isprovided to prevent the excessive swinging of the actuator 122 aroundthe center of the supporting shaft 140 to exceed the predetermined stopposition.

As shown in FIG. 4, the lower magnet 155 and the upper magnet 156 arearranged so that the north-pole magnet section 155N of the lower magnet155 and the south-pole magnet section 156S of the upper magnet 156 areopposed to each other, and the south-pole magnet section 155S of thelower magnet 155 and the north-pole magnet section 156N of the uppermagnet 156 are opposed to each other.

For this reason, fundamentally, the perpendicular magnetism in thevertical direction in FIG. 4 is created between the lower magnet 155 andthe upper magnet 156. When the voice coil 151 is located within thisperpendicular magnetism, the force (the driving force) in the horizontaldirection in FIG. 4 occurs on the voice coil 151 according to Fleming'sleft-hand rule. The actuator 122 is swung around the center of thesupporting shaft 140 in accordance with this driving force.

FIG. 5 is an enlarged view of the magnetization centers 158 and 159 ofthe upper and lower magnets 155 and 156. In FIG. 5, the arrow indicatesthe line of the magnetic force of the magnetism generated with themagnets 155 and 156.

As is apparent form FIG. 5, in the vicinity of the magnetization centers158 and 159 of the magnets 155 and 156, the lines of the magnetic forceare not formed exactly in the vertical direction (or the verticaldirection in FIG. 5), and the magnetic field is slightly inclined to thevertical direction.

Therefore, when the voice coil 151 passes through the region where thisinclined magnetic field is formed, the driving force generated accordingto Fleming's left-hand rule may contain not only the component in thehorizontal direction but also the component inclined to the verticaldirection (hereinafter, such a component of the driving force will becalled the unnecessary driving force). Therefore, when the unnecessarydriving force is applied to the voice coil 151, some vibration may occurin the actuator 22.

In the conventional magnetic head device 100, as shown in FIG. 1, whenthe head slider 104 is located at the innermost position Pi of the datazone, the center C of the voice coil 151 is deviated slightly upwardfrom the magnetization center 158 (the angle “T1 i” in FIG. 1 indicatesthe amount of deviation).

Moreover, as shown in FIG. 2, when the head slider 104 is located at theoutermost position Po of the data zone, the center C of the voice coil151 is deviated slightly downward from the magnetization center 158 (theangle “T1 o” in FIG. 2 indicates the amount of deviation).

The conventional magnetic head device 100 is provided such that theseamounts of deviation are set to meet the condition: T1 o>T1 i. That is,the conventional magnetic head device 100 is provided such that, whenthe head slider 104 is located at the innermost position Pi, the rightside section coil 151A (which is shown in FIG. 7) is located nearer tothe magnetization center 158 than the left side section coil 151B.

FIG. 7 is a diagram for explaining the problem of the conventionalmagnetic head device 100.

In FIG. 7, both the position (indicated by the solid line) of the voicecoil 151 on the magnet 55 when the head slider 104 is located at theinnermost position Pi, and the position (indicated by the one-dot chainline) of the voice coil 151 when the head slider 104 is located at theoutermost position Po are shown.

As shown in FIG. 7, the deviation (T2 o) between the magnetizationcenter 158 and the side section coil 151A when the head slider 104 islocated at the outermost position Po is smaller than the deviation (T2i) between the magnetization center 158 and the side section coil 151Bof the voice coil 151 when the head slider 104 is located at theinnermost position Pi (T2 i>T2 o).

Thus, in the conventional magnetic head device 100, when the head slider104 is located at the outermost position Po, the side section coil 151Ais located within the region in which the lines of magnetic forcegenerated near the magnetization center 158 are inclined to the verticaldirection.

For this reason, in addition to the horizontal force (the driving forcefor the actuator 122), the unnecessary driving force will be applied tothe side section coil 151A, and some vibrations occur on the actuator122.

Thus, when the vibrations occur on the actuator 122, the head slider 104may be impacted with the magnetic disk 101. Hence, the problem arises inthat there is the possibility that the information recorded in the datazone 132 may be damaged in the worst case.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved magneticdisk device in which the above-mentioned problems are eliminated.

Another object of the present invention is to provide a magnetic diskdevice which is capable of preventing the occurrence of vibrations inthe actuator.

The above-mentioned objects of the present invention are achieved by amagnetic disk device comprising: a magnetic disk in which a data zone isformed; an actuator having a voice coil and a head slider carrying amagnetic head, the actuator being swung to move the magnetic head overthe disk between an innermost position of the data zone and an outermostposition of the data zone; and a magnet having a magnetization centerand opposed to the voice coil so that a voice-coil motor which swingsthe actuator is formed, the magnet having a north pole and a south poleconfronting each other via the magnetization center, wherein themagnetic disk device is provided so that a deviation of a center of thevoice coil from the magnetization center when the magnetic head is inthe innermost position of the data zone is substantially equal to adeviation of the center of the voice coil from the magnetization centerwhen the magnetic head is in the outermost position of the data zone.

The above-mentioned objects of the present invention are achieved by amagnetic disk device comprising: a magnetic disk in which a data zone isformed; an actuator having a voice coil and a head slider carrying amagnetic head, the actuator being swung to move the magnetic head overthe disk between an innermost position of the data zone and an outermostposition of the data zone; and a magnet having a magnetization centerand opposed to the voice coil so that a voice coil motor which swingsthe actuator is formed, the magnet having a north pole and a south poleconfronting each other via the magnetization center, wherein themagnetic disk device is provided so that a position of a center of thevoice coil from the magnetization center when the magnetic head is inthe center between the innermost position and the outermost position ofthe data zone is substantially equal to a position of the magnetizationcenter of the magnet.

The above-mentioned objects of the present invention are achieved by amagnetic disk device comprising: a magnetic disk in which a data zone isformed; an actuator having a voice coil and a head slider carrying amagnetic head, the actuator being swung to move the magnetic head overthe disk between an innermost position of the data zone and an outermostposition of the data zone wherein the voice coil includes first andsecond side section coils; and a magnet having a magnetization centerand opposed to the voice coil so that a voice coil motor which swingsthe actuator is formed, the magnet having a north pole and a south poleconfronting each other via the magnetization center, wherein themagnetic disk device is provided so that a deviation between themagnetization center and one of the first and second side section coilsnearer to the magnetization center when the magnetic head is in theinnermost position of the data zone is substantially equal to adeviation between the magnetization center and the other of the firstand second side section coils nearer to the magnetization center whenthe magnetic head is in the outermost position of the data zone.

According to the present invention, it is possible to possible toprevent the decreasing or increasing of the deviation between themagnetization center and the center of the voice coil (which constitutespart of the voice-coil motor) when the magnetic head is located at theinnermost position of the data zone or the outermost position of thedata zone. It is possible for the magnetic disk device of the presentinvention to prevent that the magnet driving force of the magnet in theinclined direction from being applied to the voice coil. It is thereforepossible to prevent the occurrence of vibrations in the actuator.

Moreover, the magnetic disk device of the present invention may beprovided so that the north pole and the south pole of the magnet arearranged in an asymmetrical formation about the magnetization center.

Moreover, the above-mentioned objects of the present invention areachieved by a magnetic disk device comprising: a magnetic disk in whicha data zone is formed; an actuator having a voice coil and a head slidercarrying a magnetic head, the actuator being swung around a center tomove the magnetic head over the disk between an innermost position ofthe data zone and an outermost position of the data zone; and a magnethaving a magnetization center and opposed to the voice coil so that avoice coil motor which swings the actuator is formed, the magnet havinga north pole and a south pole confronting each other via themagnetization center, wherein the voice coil is arranged in a generallytrapezoidal configuration and includes first and second side sectioncoils, and the magnetic disk device is provided so that an intersectionof extension lines of the first and second side section coils isdeviated from the center of the swinging of the actuator to a locationwhere the magnetic head is arranged.

In the case of the conventional magnetic head device, the voice coil isarranged in a generally trapezoidal configuration and the intersectionof the extension lines of the side section coils of the voice coil is inagreement with the rotation center of the actuator. In contrast,according to the present invention, the magnetic disk device is providedso that the intersection of the extension lines of the first and secondside section coils is deviated from the center of the swinging of theactuator to a location where the magnetic head is arranged. Therefore,it is possible to prevent the decreasing or increasing of the deviationbetween the voice coil and the magnetization center.

For this reason, it is possible for the present invention to preventthat the magnetism of the magnet in the inclined direction to thevertical direction be applied to the voice coil, and therefore it ispossible to prevent the occurrence of vibrations in the actuator.

According to the magnetic disk device of the present invention, it ispossible to prevent the occurrence of vibrations in the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

FIG. 1 is a plan view of a conventional magnetic head device when thehead slider is located in the innermost position of the data zone of amagnetic disk.

FIG. 2 is a plan view of the conventional magnetic head device when thehead slider is located in the outermost position of the data zone of themagnetic disk.

FIG. 3 is an enlarged view of the actuator which is provided in theconventional magnetic head device.

FIG. 4 is a diagram for explaining the composition of the voice-coilmotor provided in the conventional magnetic head device.

FIG. 5 is an enlarged view of the magnetization centers of the upper andlower magnets.

FIG. 6 is a diagram for explaining the composition of the upper andlower magnets in the conventional magnetic head device.

FIG. 7 is a diagram for explaining the problem arising with theconventional magnetic head device.

FIG. 8 is a plan view of the magnetic disk device in one preferredembodiment of the present invention.

FIG. 9 is an enlarged plan view of the actuator in the magnetic diskdevice of the first preferred embodiment of the invention when the headslider is located in the innermost position of the data zone of themagnetic disk.

FIG. 10 is an enlarged plan view of the actuator in the magnetic diskdevice of the first preferred embodiment when the head slider is locatedin the outermost position of the data zone of the magnetic disk.

FIG. 11 is a diagram for explaining operation of the magnetic diskdevice of the first preferred embodiment of the invention.

FIG. 12 is an enlarged view of the actuator which is provided in themagnetic disk device of the second preferred embodiment of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A description will now be given of the magnetic disk device 10 of thefirst preferred embodiment of the invention using FIG. 8 through FIG.11.

FIG. 8 is a plan view of the magnetic disk device 10 of the presentembodiment. FIG. 9 is an enlarged plan view of the actuator 22 of thepresent embodiment when the head slider is located in the innermostposition of the data zone of the magnetic disk. FIG. 10 is an enlargedplan view of the actuator 22 of the first preferred embodiment when thehead slider is located in the outermost position of the data zone of themagnetic disk.

As shown in FIG. 8, the magnetic disk device 10 is provided with theenclosure including the covering (not shown) and the base 42. Theenclosure is configured to contain the magnetic disk 11 which is thedata recording medium, the spindle motor 12 which rotates the magneticdisk 11, the actuator 22 on which the head slider 14 carrying themagnetic head is mounted, and the voice-coil motor (VCM) 23 which swingsthe actuator 22 around the center of the supporting shaft 40.

The magnetic disk 11 is fixed to the rotor section of the spindle motor12. The rotation driving of the magnetic disk 11 is performed by thespindle motor 12 at the time of operation of the magnetic disk device 10(or at the time of recording/reproduction processing), and the rotationof the magnetic disk 11 is stopped at the time of non-operation of themagnetic disk device 10.

Moreover, the CSS (Contact Start Stop) method is used for the magneticdisk device 10 of the present embodiment. For this reason, in thenon-operating state of the magnetic disk device 10, the head slider 14(the magnetic head) is in contact with the magnetic disk 11. Therefore,the data zone 32 in which the tracks containing the data and the servoinformation recorded therein are arranged in the shape of a concentriccircle, and the stop region (or the CSS zone) 31 in which the headslider 14 is evacuated when the magnetic disk drive is in thenon-operating state are formed in the surface of the magnetic disk 11.

In the following description, the innermost position (or the boundaryposition with the CSS zone 31) of the data zone 32 will be called theinnermost position Pi, and the outermost position of the data zone 32will be called the outermost position Po.

Moreover, in the present embodiment, the CSS zone 31 is formed in themagnetic disk 11 inside the innermost position of the data zone 32.Alternatively, the CSS zone may be formed in the magnetic disk 11outside the outermost position of the data zone 32. Furthermore, in thepresent embodiment, the number of magnetic disks provided in themagnetic disk device 10 is one. Alternatively, a plurality of magneticdisks may be provided in the magnetic disk device of the presentinvention.

The actuator 22 is rotatably supported on the supporting shaft 40, whichis arranged on the base 42, such that the actuator 22 is capable ofbeing swung around the center of the supporting shaft 40. The actuator22 includes the support arm 24 and the coil arm 52, and the support arm24 and the coil arm 52 are arranged so that they are opposed to eachother on both the sides of the supporting shaft 40.

The support spring 25 which exerts spring pressure onto the head slider14 is attached to the leading edge of the support arm 24.

The head slider 14 is arranged so that the head slider 14 is opposed tothe magnetic disk 11. The magnetic head (not shown) is attached to thehead slider 14, and this magnetic head functions to record the datawhich is supplied from the control unit (which is not illustrated) ontothe track on the surface of the magnetic disk 11, and read out the datarecorded in the track and send the read-data signal to the control unit.

The head slider 14 is in contact with the CSS zone 31 in the disk innerregion of the magnetic disk 11 when the magnetic disk device 10 does notoperate, and the head slider 14 is raised over the surface of therotating magnetic disk 11 when the magnetic disk device 10 is in theoperating state.

The voice-coil motor (VCM) 23 is comprised of the upper magnet 56provided on the undersurface of the upper yoke 54, the lower magnet 55provided on the upper surface of the lower yoke 53, the voice coil 51provided in the coil arm 52, the lower yoke 53, and the upper yoke 54.

Moreover, the lower magnet 55 is comprised of the north pole magnetsection 55N and the south pole magnet section 55S, and the upper magnet56 is comprised of the north pole magnet section 56N and the south polemagnet section 56S.

And the north pole magnet section 55N and the south pole magnet section55S confront each other in the direction of the surface thereof, and themagnetization center 58 is formed at the boundary portion between thesections 55N and 55S.

Similarly, the north pole magnet section 56N and the south pole magnetsection 56S confront each other in the direction of the surface thereof,and the magnetization center 59 is formed at the boundary portionbetween the sections 56N and 56S.

In addition, for the sake of convenience of illustration, in FIG. 8through FIG. 11, the illustration of the upper yoke 54 and the uppermagnet 56 in the present embodiment will be omitted.

Moreover, unless otherwise specified, in the following explanation, thelower and upper yokes 53 and 54 will be referred to as the yoke 53collectively, and the lower and upper magnets 55 and 56 will be referredto as the magnet 55 collectively.

In the above composition of the magnetic disk device 10, the drivecurrent is supplied to the voice coil 51 from the control unit (notillustrated). The voice coil 51 is arranged in a generally trapezoidalconfiguration, and this voice coil 51 is attached to the coil arm 52.Especially in the present embodiment, the two side sectional coilportions of the voice coil 51 are called the side section coils 51A and51B. The voice coil 51 in the present embodiment is provided so that thevoice coil 51 is opposed to the magnet 55 which is arranged on the yoke53.

Next, the detailed composition of the voice-coil motor 23 in the presentembodiment will be explained using FIG. 9 and FIG. 10.

When the head slider 14 shown in FIG. 9 is in the innermost position Pi,the center C of the voice coil 51 is located in the position which isdeviated upward (in the up direction in the sheet of FIG. 9) by theangle T3 i from the magnetization center 58 (in the present embodiment,the angle T3 i indicates the amount of deviation).

Moreover, as shown in FIG. 10, when the head slider 14 is in theoutermost position Po, the center C of the voice coil 51 is located inthe position which is deviated downward (in the down direction in thesheet of FIG. 10) by the angle T3 o from the magnetization center 58 (inthe present embodiment, the angle T3 o indicates the amount ofdeviation).

The magnetic disk device 10 of the present embodiment is provided sothat the angles T3 i and T3 o which indicate these amounts of deviation)are equal to each other to meet the condition: T3 i=T3 o.

According to the magnetic disk device 10 of the present embodiment,regardless of whether the head slider 14 is located in the innermostposition Pi or in the outermost position Po, the deviation between themagnetization center 58 and the side section coil 51A of the voice coil51 and the deviation between the magnetization center 58 and the sidesection coil 51B of the voice coil 51 are equal to each other.

Next, a description will be given of the operation of the magnetic diskdevice 10 of the present embodiment using FIG. 11.

FIG. 11 shows both the position (indicated by the solid line) of thevoice coil 51 on the magnet 55 when the head slider 14 is located in theinnermost position Pi, and the position (indicated by the one-dot chainline) of the voice coil 51 when the head slider 14 is located in theoutermost position Po.

As shown in FIG. 11, in the present embodiment, the deviation T4 ibetween the side section coil 51B of the voice coil 51 (which is locatednearer to the magnetization center 58 when the head slider 14 is locatedin the innermost position Pi) and the magnetization center 58, and thedeviation T4 o between the side section coil 51A (which is locatednearer to the magnetization center 58 when the head slider 14 is locatedin the outermost position Po) and the magnetization center 58 are equalto each other to meet the condition: T4 i=T4 o.

Moreover, although not illustrated, according to the magnetic diskdevice 10 of the present embodiment, when the head slider 14 is locatedin the center (or the center between the innermost position Pi and theoutermost position Po) of the data zone 32, the position of the center Cof the voice coil 51 (the actuator 22) and the position of themagnetization center 58 of the magnet 55 are substantially in agreementwith each other.

Therefore, the magnetic disk device 10 of the present embodiment cantake the largest deviations between the side section coils 51A and 51Bof the voice coil 51 and the magnetization center 58 when the headslider 14 is located in the outermost position Po, and when the headslider 14 is located in the innermost position Pi.

Although the magnetic field is generated at the magnetization center 58in the inclined direction as described previously, it is possible toprevent the inclined magnetic field from being applied to the voice coil51 because the increasing or decreasing of the deviations between themagnetization center 58 and the side section coils 51A and 51B can beavoided.

According to the magnetic disk device of the present embodiment, it ispossible to prevent the occurrence of vibrations in the actuator 22, andtherefore the problem that the information recorded on the data zone 32may be damaged as in the conventional magnetic head device can beprevented.

Next, a description will be given of the magnetic disk device of thesecond preferred embodiment of the invention using FIG. 12. FIG. 12 isan enlarged view of the actuator 30 of the magnetic disk device of thesecond preferred embodiment.

In the following, only the actuator 30 of the present embodiment will bedescribed. Other composition of the magnetic disk device of the presentembodiment except for the actuator 30 is essentially the same ascorresponding composition of the magnetic disk device 10 of the firstpreferred embodiment, and a description thereof will be omitted for thesake of convenience.

As previously described with FIG. 3, the conventional magnetic headdevice 100 is constituted so that the intersection of the extensionlines (indicated by the arrows B1 and B2) of the side section coils 151Aand 151B of the voice coil 151 is in agreement with the rotation center(or the center of the supporting shaft 140) of the actuator 122.

On the other hand, the magnetic disk device of the present embodiment isconstituted so that the intersection B of the extension lines D1 and D2of the side section coils 51A and 51B of the voice coil 51 is deviatedfrom the swinging center A of the actuator 30 to the location (in theupward direction in FIG. 12) where the magnetic head is arranged.

Specifically, the position of the intersection B of the extension linesof the side section coils 51A and 51B is shifted from the swingingcenter A of the actuator 30 to the side where the magnetic head isarranged by the distance dL as indicated in FIG. 12.

According to this composition, the positions of the extension lines D1and D2 of the voice coil 51 can be extended outside in comparison withthe positions of the extension lines B1 and B2 of the coil 151 in theconventional device in which the intersection A is located at theswinging center A of the actuator 30.

In the embodiment of FIG. 12, the positions of the extension lines D1and D2 are outwardly shifted by the distance dW from the positions ofthe extension lines B1 and B2 in the conventional device.

Accordingly, when the head slider 14 is located in the innermostposition Pi of the data zone 32, or the outermost position Po of thedata zone 32, it is possible to separate the position of the voice coil51 (the side section coils 51A and 51B) from the position of themagnetization center 58.

Therefore, it is possible for the magnetic disk device of the presentembodiment to prevent that the slanting magnetic field formed near themagnetization center 58 be applied to the voice coil 51 (the sidesection coils 51A and 51B), thereby preventing the occurrence ofvibrations in the actuator 22.

In the present embodiment, the composition in which the upper magnet isprovided in the upper yoke and the lower magnet is provided in the loweryoke respectively has been described as an example. Alternatively, thecomposition may be modified such that the magnet is provided in eitherthe upper yoke or the lower magnet.

The present invention is not limited to the above-described embodiments,and variations and modifications may be made without departing from thescope of the present invention.

1. A magnetic disk device comprising: a magnetic disk in which a datazone is formed; an actuator having a voice coil and a head slidercarrying a magnetic head, the actuator being swung to move the magnetichead over the disk between an innermost position of the data zone and anoutermost position of the data zone; and a magnet having a magnetizationcenter and opposed to the voice coil so that a voice coil motor whichswings the actuator is formed, the magnet having a north pole and asouth pole confronting each other via the magnetization center, whereinthe magnetic disk device is arranged so that a deviation of a center ofthe voice coil from the magnetization center when the magnetic head isin the innermost position of the data zone is made equal to a deviationof the center of the voice coil from the magnetization center when themagnetic head is in the outermost position of the data zone.
 2. Themagnetic disk device according to claim 1 wherein the north pole and thesouth pole of the magnet are arranged in an asymmetrical formation aboutthe magnetization center.
 3. A magnetic disk device comprising: amagnetic disk in which a data zone is formed; an actuator having a voicecoil and a head slider carrying a magnetic head, the actuator beingswung to move the magnetic head over the disk between a First positionand a second position; and a magnet having a magnetization on center andopposed to the voice coil so that a voice coil motor which swings theactuator is formed, the magnet having a north pole and a south poleconfronting each other via the magnetization center, wherein themagnetic disk device is arranged so that a deviation of a center of thevoice coil from the magnetization center when the magnetic head is inthe first position is made equal to a deviation of the center of thevoice coil from the magnetization center when the magnetic head is inthe second position.
 4. The magnetic disk device according to claim 3,wherein the north pole and the south pole of the magnet are arranged inan asymmetrical formation about the magnetization center.